waterproof brick coating

Good morning all,
We have just bought an old cottage with a cement render that is shot,it is cracked and very porous and is causing damp patches in the living areas as it is trapping water between it and the very soft bricks,as it is single course the water is just soaking through the bricks.We have decided to have all this render removes and we can then examine the brickwork to decide if we can have it all pointed up ,or as we suspect previous alterations have left a legacy of ismatched bricks and blocks,in which case we will have it all re rendered,when the existing render is removed and the brickwork dries out what is the best liquid waterproofer we can apply before it is re rendered?many thanks for your help,Bob

I would think you would be very well advised to look at external
insulation before rendering. And then a proper damp proof membrane can
be install between the insulation and the brick. You can probably get a
grant for much of the extra cost.
TOF.

Yes, that might well work.
thinking about what was done here to a timber frame, something like
nailing vertical battens over a breathable DPM to the walls, infilling
with celotex, and then horizontals with more infilling then vertical
battens and a metal lathe rendered over..
Of course that might make the roof not fit :-)

--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to

The wall was probably saturated because it was rendered. Water vapour from inside migrates through the wall.
When it hits the cold outer surface, in winter, the vapour condenses into water. It usually evaporates, . If the wall is rendered, it can't pass through the cement render and can't evaporate.
It accumulates in the brickwork. Look up 'interstitial condensation'.
You paint on waterproof crap, the same thing will happen. It's like putting on a waterproof coat when it's raining; you end up saturated in your own sweat because it can't evaporate.
I don't think they do Goretx for houses.

cracked and very porous and is causing damp patches in the living areas as it is
trapping water between it and the very soft bricks,as it is single course the
water is just soaking through the bricks.We have decided to have all this render
removes and we can then examine the brickwork to decide if we can have it all
pointed up ,or as we suspect previous alterations have left a legacy of
ismatched bricks and blocks,in which case we will have it all re rendered,when
the existing render is removed and the brickwork dries out what is the best
liquid waterproofer we can apply before it is re rendered?many thanks for your
help,Bob

water. It usually evaporates, . If the wall is rendered, it can't pass through
the cement render and can't evaporate.

on a waterproof coat when it's raining; you end up saturated in your own sweat
because it can't evaporate.

so lacking in actual understanding as to be almost complete twaddle

--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to

cracked and very porous and is causing damp patches in the living areas as it is
trapping water between it and the very soft bricks,as it is single course the
water is just soaking through the bricks.We have decided to have all this render
removes and we can then examine the brickwork to decide if we can have it all
pointed up ,or as we suspect previous alterations have left a legacy of
ismatched bricks and blocks,in which case we will have it all re rendered,when
the existing render is removed and the brickwork dries out what is the best
liquid waterproofer we can apply before it is re rendered?many thanks for your
help,Bob

water. It usually evaporates, . If the wall is rendered, it can't pass through
the cement render and can't evaporate.

putting on a waterproof coat when it's raining; you end up saturated in your own
sweat because it can't evaporate.

damp is simply a matter of more moisture getting in than getting out.
It is not as simple as saying 'let it get out through porous walls' it
is equally as specious to say 'stop it getting in by making walls
impermeable'.
You get rid of damp by not letting it in, and breathing or ventilating
what is generated inside.
The modern approach is to create an utterly impervious insulated shell
and VENTILATE the interior adequately. Th reason is this works BETTER
than breathable walls.
All this twaddle about breathable walls arises from not understanding
that some older houses stayed dry because they were built like
sponges.,. That doesn't make it a good thing to do. It merely highlights
the fact that if you coat a sponge house with a plastic mac it will be
damp until you arrange proper ventilation.

--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to

Also, what was relatively waterproof 100 years ago may not be now. The
lime mortar in most old houses has degraded to a point where it is
little better than sand.
I don't know what the chemistry of the degradation is, but the idea that
it somehow heals itself doesn't apply to any lime mortar that I'm
familiar with

I believe the long term change in lime mortar is the lime (calcium hydroxide) turning to calcium carbonate; i.e. the principal constituent of limestone. This squares with some of the old lime mortar I've met with being considerably harder than relatively new mortar. The suggestion I've seen is that weak mortar in old houses is due to the original builders scrimping on materials and not putting enough lime in in the first place - possibly, in damp conditions, aggravated by a certain amount of leaching of the lime before it's converted to carbonate. They may also have used other materials than sand and lime to bulk out the mortar, and what those may do long term is pretty much impossible to predict.

AIUI the idea with lime mortar is that only the surface is converted to
carbonate, and this forms a surface skin to prevent the rest of the
mortar being converted. This explains why the mortar survives in Roman
buildings with walls 2 feet thick but fails in 9" Victorian walls

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